Four of the 16 GOP presidential hopefuls -- Ted Cruz of Texas, Marco Rubio of Florida, Lindsey Graham of South Carolina and Rand Paul of Kentucky -- come from the Senate, which can offer a unique and powerful launching pad not available to the other candidates, something Barack Obama used to his advantage in 2008.
That dynamic was on full view in recent days when Cruz lashed out at Sen. Mitch McConnell of Kentucky, accusing the majority leader of lying
about whether he had cut a deal with Democrats to allow a vote to revive the Export-Import Bank, a federal institution that Cruz abhors.
"There is profound disappointment among the American people because we keep winning elections and they keep getting leaders who don't do anything they promised," Cruz charged, tapping into the concerns of many grassroots conservatives that McConnell and House Speaker John Boehner are too mainstream to lead the modern party.
People close to McConnell won't let on just how angry he is about being called a liar by a junior senator in a speech that shattered expectations of decorum in the usually dignified chamber. They just point to McConnell's ever-present calm demeanor and say he is accustomed to dealing with strategic, tactical and political differences with members of his caucus -- whether or not they are running for president -- even when he agrees with them on the underlying policy. Like Cruz, he opposes the Export-Import Bank, for instance.
On the floor Monday, McConnell made only passing reference to the weekend's drama when speaking about completing work soon on the highway funding bill to which the Export-Import Bank issue is attached.
"We've had to navigate some especially difficult political terrain to get this far already," he said with a light chuckle. "It hasn't always been easy."
In May, when McConnell was trying to extend parts of the Patriot Act, Paul seized the floor for more than 10 hours
, railing against the National Security Agency's surveillance programs as an affront to privacy rights.
"There comes a time in the history of nations when fear and complacency allow power to accumulate and liberty and privacy to suffer. That time is now and I will not let the Patriot Act, the most unpatriotic of acts, go unchallenged," Paul said during that speech.
Paul's campaign used the issue -- and the considerable buzz it generated in the press and social media -- to raise money for his White House run.
Rubio, who sits on the both the intelligence and foreign relations committees, has used those posts to blast the Obama administration's handling of Iran and Cuba. But he has complicated McConnell's Senate math by missing many votes this year as he has been on the road fundraising and campaigning.
Graham has also been highly vocal on national security issues before the Senate, such as the Iran nuclear deal and the administrations' handling of ISIS.
The lying charge, made Friday in a forceful floor speech, stunned establishment Republicans for its brashness but didn't necessarily surprise them. That's because Cruz and other Senate Republicans seeking the White House are routinely using the Senate floor as a perch from where to pump up their sagging campaigns.
"We've thought for some time we would have to be dealing with some of the theatrics of having a lot of people running for national office. I don't think it's any particular surprise," said Sen. John Thune, R-South Dakota, the third-ranking Republican leader and a McConnell ally. "Obviously, when people are trying to give oxygen to their presidential campaigns, they're going to be inclined to support agendas on the floor of the Senate that might not always be consistent with what we're trying to get accomplished."
McConnell may need thick skin to weather the criticism from fellow Republicans, and patience to wait out their high-profile floor maneuvers. But the best tools he has to blunt them are his expertise in legislative politics and strategies and the strong support of most of his caucus.
For instance, after Cruz's attack Friday, McConnell and his aides didn't say a word. Instead, they prepared quietly for a series of votes on a rare Sunday session when they approved the Export-Import Bank and cut off an effort by Cruz to change Senate rules. In a rarely seen move, GOP leaders convinced virtually all Republicans to not even grant Cruz a roll call vote on his measure, a sign of the influence McConnell has over his caucus even as Cruz garners presidential headlines.
In a calculated move, McConnell dispatched Utah Sen. Orrin Hatch, the chamber's most senior Republican, to rebuke Cruz and the other junior senators running for president and to remind them to mind manners when they are in the Senate.
"This is a high and holy calling. It is not something to take lightly. It is a sacred trust in which pettiness or grandstanding should have no part," Hatch said. "In some respects, the Senate today is but a mere shadow of its former self, another casualty of the permanent political campaign."
Veteran observers of the Senate, even Democrats, recognize what McConnell is up against.
"You have to add into it the factor that only the top 10 are going to the debates," Sen. Dick Durbin of Illinois, a Democratic leader, told CNN. "That creates an incentive for anyone not in the top 10 to make a splash, make news, and that's not good for the Senate and not good for Senator McConnell's agenda. As they want to get in with extraneous issues to try to break from the pact."
John Ullyot, a former longtime Senate Republican aide who is now a political and communications strategist, said Cruz's "throwing bombs" in the Senate fires up his political base.
"He's trying to run for president, so his target audience is people who are frustrated with Washington. He's got a safe seat so he doesn't have to answer to anybody. There is no downside to him for throwing bombs at Senate leadership and that's got to be very frustrating for Sen. McConnell and others in the Republican leadership," Ullyot said.
Ullyot predicted there will be more of the same in the months ahead.
"You'll get a constant stream of clashes between the candidates running for president and the majority leader because they are going to want to see action and pick fights" on issues that McConnell is trying to move on the floor, Ullyot said. "He doesn't want a lot of heated rhetoric, particularly not against him and his fellow leaders."