Republican presidential front-runner Donald Trump rallied supporters in Madison, Miss., on March 7, on the eve of the state’s presidential primary. (AP)

Donald Trump continues to lead his rivals nationally in the contest for the Republican presidential nomination. But his hold on the GOP electorate has weakened since the primary season began, and the party is now deeply divided over his candidacy, according to a new Washington Post-ABC News poll.

Trump maintains the support of 34 percent of registered Republicans and Republican-leaning independents, compared with 25 percent for Sen. Ted Cruz of Texas, 18 percent for Sen. Marco Rubio of Florida and 13 percent for Ohio Gov. John Kasich.

Trump’s margin over Cruz has narrowed from 16 points in January to nine today. As a succession of Republican candidates quit the race, Cruz’s position has ticked up four points since January, Rubio’s has risen by seven and Kasich’s has grown by 11. Trump’s has dipped by three points, within the poll’s margin of sampling error.

In the Democratic race, former secretary of state Hillary Clinton still leads Sen. Bernie Sanders of Vermont, but her national margin is the smallest in a Post-ABC poll since the beginning of the campaign. The new poll shows Clinton as the favorite of 49 percent of registered Democrats and Democratic-leaning independents compared with Sanders, whose support is at 42 percent. That seven-point lead for Clinton compares with her 19-point advantage in January.

That Trump is a polarizing figure within the Republican Party is no surprise, and it’s typified by the opposition among establishment and other Republicans that has intensified over the past few weeks. Only a bare majority (51 percent) of Republicans or Republican-leaning independents say they would be satisfied with the New York billionaire as their nominee, a noticeably smaller percentage than for Cruz (65 percent) or Rubio (62 percent), with Kasich in between at 56 percent.

Favorable ratings also indicate an increasingly tenuous standing within the party. In early January, Republicans clearly gave Trump more favorable than unfavorable reviews, 60 percent to 39 percent. That has narrowed to a 53-46 margin, with negative marks at their highest level in Post-ABC polling since Trump entered the race. His positive ratings also trail Cruz’s 64 percent and Rubio’s 63 percent.

The Post-ABC poll finds that more than half of Republicans and GOP-leaning independents think Trump is dishonest, does not understand their problems, lacks the right experience, and does not have the right personality and temperament to be an effective president. By contrast, more than 6 in 10 Republicans say Cruz is honest, empathetic, and has the right temperament and experience; similar shares say Rubio has the first three qualities, while half say he has the right experience.

In a hypothetical head-to-head test of strength between Trump and Cruz, Republicans say they prefer the senator by 54 percent to 41 percent. Rubio is a narrower favorite in a one-on-one test against Trump, with an edge of 51 percent to 45 percent. The survey did not test a Trump-Kasich face-off.

The poll was conducted over a weekend in which Cruz won contests in Kansas and Maine, Trump won in Louisiana and Kentucky, and Rubio won in Puerto Rico. On Tuesday, Republicans are voting in Michigan, Mississippi, Idaho and Hawaii.

Next Tuesday — the first day states can award delegates on a winner-take-all basis — there will be contests in Florida, Ohio, Illinois, Missouri and North Carolina. By the end of that day, more than half of the 2,472 convention delegates will have been awarded.

It is likely that, after those March 15 contests, Republicans will have the clearest sense yet of Trump’s overall strength and of the viability of his challengers. Cruz’s string of recent victories, including in his home state of Texas a week ago, have elevated him as the leading rival to Trump. If Rubio and Kasich don’t win their home states, they will face pressure to quit the race.

Many now predict that the Republican contest will not be resolved before the national convention in July. But even many Republicans who say they would not be satisfied with Trump as the nominee appear uneasy about the efforts of party leaders to prevent him from winning. About half of all Republicans who are dissatisfied or only “somewhat satisfied” with Trump nonetheless oppose efforts by party leaders to prevent him from becoming the nominee.

There is considerable talk now about a possible floor fight at the convention, should Trump arrive with the most delegates but lacking the 1,237 needed for a first-ballot victory. About 42 percent of Republican voters support other candidates and say that in such a situation, the party should pick another nominee. But 53 percent either support Trump or say that leading the delegate count, even if short of an outright majority, should guarantee victory.

Among all Americans, Trump has a more negative image by far compared to Cruz, Rubio or Clinton. Two in 3 adults say they have an unfavorable impression of Trump, who has drawn controversy in recent months for attacks on illegal immigrants from Mexico, Sen. John McCain of Arizona, Fox News anchor Megyn Kelly, a disabled reporter and Muslims, among other targets.

None of the three other candidates tested — Clinton, Cruz and Rubio — had a net positive image, but all were viewed more favorably than Trump. Among all adults, 52 percent say they see Clinton unfavorably, 51 percent see Cruz negatively and 45 percent have a negative impression of Rubio. Clinton and Rubio have the least-negative image overall.

The new Post-ABC survey shows a huge gender gap in support for Trump’s candidacy. He leads among Republican men with 44 percent, a roughly 2-1 margin over second-place Cruz. Among Republican women, though, he is the favorite of just 24 percent. In January, his support among GOP women stood at 37 percent, compared to 15 percent for Cruz. Trump also has lost ground against Cruz among very conservative Republicans and among those with incomes less than $50,000.

Matched against his remaining rivals, Trump continues to perform slightly better among Republicans without college degrees than among those who are university graduates, although he has an edge with both groups. He has a wider lead among voters younger than 50 than with older voters. Among white evangelical Christians, Trump narrowly trails Cruz, but among non-evangelicals and white Catholics, his lead is almost 2 to 1.

Matched directly against Cruz, though, Trump loses voters with or without college degrees, voters who see themselves as working class and middle class, and those with higher or lower incomes. Trump also loses conservatives against Cruz, especially those who say they are “very conservative,” while the two tie among moderate and liberal Republicans.

Overall, Americans remain deeply pessimistic about the federal government. Two in 3 offer negative reactions, including about a fifth who describe themselves as angry. Trump has tapped into that mood — the more dissatisfied that people are with the federal government, the more likely they are to support his candidacy.

A similarly strong majority sees the political system today as dysfunctional, even slightly more so than in the fall. Trump does best among those who feel most strongly about the way the system works.

More Americans by far say they favor someone with experience in the system as the next president, rather than someone from outside the political establishment. Republicans, though, tilt more toward an outsider. Among those who want someone from the outside, Trump has the support of nearly half. Among those looking for someone with experience, Trump runs fourth behind Cruz, Rubio and Kasich.

A similar pattern holds for two of Trump’s most controversial ideas — deporting all of the roughly 11 million illegal immigrants living in the United States and temporarily banning Muslims from entering the country as a security precaution. Overall, Americans oppose both proposals, though more Republicans favor than oppose them. Trump has big leads among those who support such policies, but those leads disappear among those who do not.

The Post-ABC poll was conducted March 3 to 6 among a random national sample of 1,000 adults reached on land-line and cellular phones. The margin of sampling error for overall results is plus or minus 3.5 percentage points.

Emily Guskin contributed to this report.