A new NBC News poll shows growing support for presumptive GOP nominee Donald Trump.

The NBC News/SurveyMonkey Weekly Election Tracking poll shows a majority of Republican and Republican-leaners who say they are registered to vote trust Donald Trump over Speaker Paul Ryan to lead the GOP.

Nearly six in 10 trust the presumptive Republican nominee to lead the Republican Party over the House speaker, while nearly four in 10 trust the speaker more.

The survey also found Sen. Bernie Sanders, who currently trails Hillary Clinton for the Democratic nomination, continues to fare better in a hypothetical November match up with Trump.

Sanders bests Trump by 12 points - 53 to 41 - according to people polled. But the NBC News/SurveyMonkey tracking poll shows Clinton prevailing over Trump by just three points - 48 to 45 - in a possible November showdown.

The poll was conducted online from May 9 through May 15, and gathered data from 14,100 adults, including 12,507 registered voters.

"Pollsters are saying polls taken now have a little bit more substance than polls taken back in January or February," said Lilly Goren, a professor of political science at Carroll University.

Goren noted both Trump and Ryan have been in the news of late, after a meeting between the two last week. So she said it makes sense both men would be prominently on Republican voters' minds.

But Goren also said the question voters were asked is very open ended - not specifying how or in which areas Ryan or Trump should be trusted to lead the GOP over the other.

"Are they talking about leading the Republican Party in a campaign? Leading the party in regards to policy?" she said.

Prof. Charles Franklin, Director of the Marquette Law School Political Poll, said the poll doesn't necessarily reflect the view of Republicans in Ryan's home state or district.

"We've seen in the polling that has been done that, in Ryan's district, he remains very popular," Franklin said.

Franklin also said it's likely that more "establishment" Republicans, like Ryan, will continue to coalesce behind Trump now that he's won the nomination. Franklin said whether Ryan officially endorses Trump remains to be seen.

"A Paul Ryan endorsement would show that the Capitol Hill establishment is now willing to accept Trump as the nominee," Franklin said.

Franklin added voters nationally could be less trusting of Ryan because they tend to distrust the U.S. Congress as a whole.

"You see congressional leadership, especially Paul Ryan, as the subject of a lot of criticism over the last year, and that takes a toll on his overall support as Speaker of the House," Franklin said.

In downtown Milwaukee, voters said they're still not sold on Trump's candidacy.

"I don't know if he's got some ulterior motive or if he actually cares," said voter Shea Royal. "I do believe he'd hire the right people for the right jobs in his administration."

"It's just the honesty thing," said voter Larry Balestreri. "I think Trump's got a ways to go to prove he's genuine."

Balestreri added he also doesn't trust Hillary Clinton, but has a very high opinion of Ryan.

"Wisconsin is a state that backs somebody that works hard and is honest, and I think (Ryan) fits those two profiles," he said.