"This is the most important election of our lifetime." It's a cliché, a speechwriter's placeholder, rhetorical white noise.

In this tumultuous year, though, the phrase beloved by campaigning politicians might seem a little less absurd than usual.

Consider the setting and the stakes for this year's presidential contest:

Outrage and civil unrest continue across the nation after police killings of two more black men, and then a gunman slaughters five Dallas police officers during a peaceful Black Lives Matter protest. Another terrorist attack in France reminds us of our vulnerability.

Millions of Americans feel they're struggling just to pay the bills, despite an economic recovery that looks good on paper. Plenty consider the political system broken and the nation's leaders deaf to their concerns.

Amid this context, Election Day will effectively decide control of all three branches of the federal government.

Beginning Monday, Republicans will gather in Cleveland to nominate Donald Trump, a brash and combative real estate investor from Manhattan with no political experience. He argues that "weak leadership" for the last eight years has sapped U.S. strength. He vows to restore it.

Trump speaks to those he calls the "silent majority" - a phrase also used by President Richard Nixon in 1968. He promises to build a wall with Mexico, deport 11 million immigrants here illegally, rip up unfair international trade deals that have cost jobs, and bar Muslims from entering the country.

The following week, in Philadelphia, Democrats are set to nominate Hillary Clinton, the former first lady, U.S. senator, and secretary of state under President Obama. She's a technocrat, fluent in policy, who believes in the power of government to improve the lots of ordinary Americans.

Clinton, who would be the first female president, wants to build on the successes of the Obama administration. She says dangerous times require a steady hand and a rational mind in the Oval Office, and she's attempting to portray Trump as unqualified by temperament and ignorance.

Here's the other seasoning in the electoral stew: Clinton and Trump are the two most disliked major-party nominees in the history of modern polling. Majorities of voters believe that Clinton, who faced an FBI investigation into her handling of classified material on a private email server as secretary of state, is untrustworthy and that Trump is divisive, with his pattern of misogynistic and ethnically insensitive remarks.

Clinton was not charged in the email matter. Polls show she has been a polarizing figure in politics for more than two decades.

"We have become accustomed to high levels of mutual disapproval between political partisans," William A. Galston, a Brookings Institution scholar and former aide to President Bill Clinton, argued in a paper last week.

"This year, disapproval is high within as well as between partisan ranks, setting the stage for what promises to be one of the most negative campaigns that any of us has ever experienced," Galston said.

Negative campaigns tend to depress voter turnout, but a Pew Research study last week found that 85 percent of respondents reported they were following the news about the presidential candidates very or fairly closely, the highest level in a quarter century.

And 74 percent believe it "really matters" who wins the election in terms of making progress on important problems facing the country, Pew says.

To Galston, those numbers suggest the possibility of a high participation rate Nov. 8. He said people "will come out in droves to vote against the candidate they despise."

At any rate, a CBS/New York Times poll last week found 61 percent of registered voters agreeing they are not looking forward to the next few months of the presidential campaign. Clinton and Trump voters were about equal in the sentiment. (At least there's unity in that.)

Still somebody will win, and that person could have the opportunity to appoint three to five justices to the Supreme Court, considering likely retirements from the bench. That would set the court's ideological course for a generation.

After losing the Senate in difficult political circumstances two years ago, Democrats are hoping to turn the tables this year, taking advantage of a favorable map in which they are defending fewer vulnerable incumbents, the typically higher turnout in a presidential election year - especially in swing states such as Pennsylvania, and Trump's name atop the GOP ticket.

Democrats need five seats to take control - four if they win the White House, as the vice president would break the tie. They are targeting Republican incumbents in places Obama carried in 2012, including Pennsylvania, Illinois, Ohio, New Hampshire, and Florida. At every turn, Democrats try to link Republicans to Trump. The GOP wants to localize the Senate races.

In most presidential campaigns, candidates get a polling bump from their conventions, among the few campaign events voters tune in to en masse. Early polls have seesawed in this race, with Clinton dipping a little nationally and in several swing states recently because of the email controversy.

Democrats have signaled they will use their convention as an all-out assault on Trump's record and to remind critical constituencies, such as minority voters, of what they see as detrimental consequences should the mogul be elected.

Republicans get to go first, though, and strategists say that Trump's first imperative will be to try to stitch together as much of the GOP coalition as he can, after his populist-tinged insurgency alienated many conservative activists and center-right establishment figures. He took a step in that direction last week by naming as his running mate Indiana Gov. Mike Pence, who has strong ties to evangelicals and, as a former House member, to the party's congressional wing.

"Clinton might be ahead, but she has problems, too," said Alan Novak, former chairman of the Pennsylvania GOP and a party strategist. "Her trust issues are going to remain. . . . Both of these candidates need the conventions desperately, and they need to come out of their conventions with some kind of momentum."

The worry for Team Trump is that it has lagged behind Clinton in fund-raising and in building an organization capable of generating the votes that could be critical in competitive states. Trump has relied on his mastery at getting media coverage and large rallies.

"Has he shown any inkling of putting together a modern campaign? I don't see it," said Christopher Nicholas, a GOP consultant based in Harrisburg. "All of the polling says if he ran a good campaign he could win, but it's an absolute disaster."

GOP strategist John Brabender said that Trump has mined the seam that former Pennsylvania Sen. Rick Santorum opened to Republicans in his 2012 presidential run: working-class white voters.

"Rick beat Mitt Romney in 11 states in the rural areas and small towns, where people were disaffected," said Brabender, a Pittsburgh native who ran Santorum's campaign. "The irony is that it's taking a billionaire to galvanize all that."

Brabender said Trump's challenge now will be to capture and hold moderate suburban voters in swing states like Pennsylvania, to go along with his base.

"He's most vulnerable with moderate Republican women," Brabender said. "That's the target."

215-854-2718@tomfitzgerald

Washington correspondent Jonathan Tamari contributed to this article.