Harry Reid Says GOP Is to Blame for Donald Trump as Republicans Distance Themselves From Front-Runner Meanwhile, the list of Republicans distancing themselves from Trump is growing.

 -- Nevada Sen. Harry Reid had some strong words for not only Donald Trump but also for members of the so-called Republican establishment, whom he accused of "waffling" about the party's presumptive nominee.

The Senate minority leader blasted his Republican colleagues during a speech on the Senate floor Monday, arguing that Trump's expected nomination comes after years of work by a party that Reid says excluded groups of voters.

"He's no accident. His nomination is not some mistake. Donald Trump is the natural evolution of a party that spent eight years honing a platform that is anti-immigrant, anti-woman, anti-Obama and anti-working people," Reid said.

He added: "He's the nominee of the Republican Party, but it's the nominee the Republican leaders deserve.... Republican senators need to say whether they’re going to vote for this guy. The Republican Party’s chickens have come home to the roost in the form of Donald Trump."

That said, the list of Republican leaders distancing themselves from Trump is growing.

Florida Sen. Marco Rubio, who dropped out of the presidential race in February, made it clear that he does not want to be considered as a vice presidential candidate.

Rubio wrote on Facebook Monday that his "previously stated reservations about [Trump's] campaign and concerns with many of his policies remain unchanged."

Meanwhile, New Hampshire Sen. Kelly Ayotte said today that she would vote for "our Republican nominee," but noted to local station NH1 that she doesn't plan to make any endorsements.

Senate Majority Leader Mitch McConnell took a similar path today as well, saying that Trump will likely be the Republican nominee -- and McConnell wants the nominee to win.

“I think most of my members believe he's won the nomination the old-fashioned way; he got more votes than anybody else, and we respect the voices of the Republican primary voters across the country. And we'll sit down and talk about the way forward,” McConnell said of the GOP leaders’ meeting with Trump this Thursday.

Rubio and Ayotte's statements come after a number of notable Republicans have shown they're hesitant to support their party's presumptive nominee.

President George H.W. Bush and his son President George W. Bush said last week they have no plans to endorse Trump, while Speaker of the House Paul Ryan told CNN's Jake Tapper Thursday that he's not ready to endorse Trump either.

James Campbell, a professor of political science at the University of Buffalo, told ABC News that enthusiasm for Trump among the party's higher-ups is tepid at best.

"After months of [Trump] trashing the party's establishment, I think this was to be expected and is understandable," Campbell said.

He added: "For Republicans, a long national nightmare still has a long way to go."

ABC News’ Alana Abramson and Ali Weinberg contributed to this report.