A national poll from Monmouth University released Monday finds that Hillary Clinton is the top choice of Democrats as the party's 2016 presidential nominee, though a substantial number also think she should be challenged in a primary.

When asked who they'd like to see as the party's candidate, 48 percent of respondents volunteered Clinton's name, to 6 percent for Massachusetts Sen. Elizabeth Warren, and 2 percent each for Vermont Sen. Bernie Sanders and Vice President Biden.

"When nearly half of Democratic voters volunteer the name Hillary Clinton as their choice for 2016, it's hard to deny that she is the clear front runner," said Patrick Murray, director of the Monmouth University Polling Institute in West Long Branch, N.J.  "At the same, time Democrats do not want to the nomination process to be a coronation."

The poll asked participants to name a preferred candidate without providing a list of names from which to choose. Six in 10 expressed a preference, while 32 percent said they are undecided at this point, and 7 percent said they didn't plan to support a Democrat for president in 2016.

About 4-in-10 (43%) Democratic voters thought it would be wise for the party to coalesce behind Clinton, the former first lady, secretary of state and U.S. senator from New York, early in the nominating process. But more – 48 percent said it would be better for the party if she faced an active primary challenge.

Democratic men (56%) were more likely than women (42%) to prefer a contested nomination.  While most self-professed Clinton supporters (53%) would like to see the field cleared for her, a significant number (41%) would actually like to see their favored candidate tested by competition.

Monmouth University conducted telephone interviews with 1,008 U.S. adults over age 18 between Dec. 10 and Dec. 14.

The poll results are based on a sample of 386 registered voters who identify themselves as Democrats or as leaning toward the Democratic Party.  The findings are subject to a margin of error of plus-or-minus 5 percentage points.

On Tuesday, the university's polling institute plans to release results for the 2016 Republican presidential race.