When Sen. Rand Paul floated a bill to soften Environmental Protection Agency regulation of ethanol, he had eyes on Iowa voters.
In his presidential-campaign kickoff speech, Sen. Ted Cruz appealed to social conservatives by saying the government should protect the "sacrament of marriage"—and he's got legislation to ensure states can block gay marriage within their borders.
And when Sen. Marco Rubio talks up the sweeping tax plan he wrote with conservative Sen. Mike Lee, which includes new $2,500 child tax credits, he's both making a pitch to struggling parents and arguing that he can make the economy grow faster.
If any of these proposals make it to the Senate floor, even if only for debate, these presidential contenders will have generated a useful talking point to roll out on the trail.
And that underscores the challenge facing Senate Majority Leader Mitch McConnell this year as he both manages a chamber with a must-pass agenda and maneuvers to help his party win the White House.
"The Senate floor is going be used as a campaign platform for these senators in terms of voting for amendments, making high-profile floor speeches on certain issues, and, frankly, using it to rally against Washington," said Republican strategist Ron Bonjean, a former senior GOP leadership aide.
As many as four Republican senators—Lindsey Graham of South Carolina included—are either running or considering a campaign. And each has a list of legislative priorities, some shared by McConnell and others not.
For instance, in an op-ed last year, Cruz called for continued efforts to repeal Obamacare, Common Core education standards, and EPA coal regulations, and for passing a balanced-budget amendment (a goal his 2016 rivals share), among other things.
Paul, in his campaign launch speech, offered ideas on everything from passing a "read the bills" act to reining in NSA surveillance. Rubio's own launch speech was softer on details, but he has introduced a suite of bills already this year that take conservative stances on parental notification of abortion, gun rights, school choice, and more.
But it's McConnell's office that decides which issues get valuable floor time and the attention of leadership's messaging operations. How the majority leader chooses to allocate that time among his party's 2016 contenders could have an effect on those campaigns' ability to credibly point to their experience and policy expertise.
Harry Reid dealt with the same problem during the 2008 election cycle, when, as majority leader, he had four senators in his caucus running for president: Hillary Clinton, Joe Biden, Christopher Dodd, and freshman Barack Obama. Reid opted to try to avoid the appearance that he was giving any of those candidates a leg up on any given issue.
"We were under strict orders on issues relating to both policy and media to deal with everyone as fairly as we could—no playing favorites," recalls Jim Manley, who was a senior aide to Reid and now heads the communications practice at QGA Public Affairs. "It wasn't easy, and even when we thought we treated everyone fairly, we sometimes got blowback from one office or another."
Now, with the 2016 race already underway, McConnell will grapple not only with four of his senators trying to draw contrasts against one another, but also with many of them attempting to demonstrate they are willing to buck leadership as they court conservative activist voters outside Washington.
Of greater concern for McConnell, however, is how these senators behave when the Republican-led Congress takes up critical or must-pass bills on politically sensitive topics such as the debt ceiling and federal spending.
One feature of McConnell's tenure as majority leader might make things easier for him. So far, he has been less controlling of the amendment process than Reid. "McConnell saves himself the energy of having to have a myriad of meetings with senators on whether or not amendments will be considered," Bonjean said.
But McConnell faces another challenge when the candidates are out campaigning: being prepared for the times when he'll need every member in Washington.
"The majority leader is going to need their votes on important issues," says former Senate Majority Leader Trent Lott. "It gets to be a logistical problem."
To be sure, this dynamic is hardly new, and Don Stewart, a spokesman for McConnell, downplayed the challenge. "There have been senators running for president forever. This isn't a new thing; it's not new to the leader," he said.
But that doesn't mean it won't be difficult. Having three or four of his 54 members on the campaign trail can be a problem when they're needed in the Capitol.
And with not a vote to spare en route to 60, campaign positioning could make McConnell's job even harder, noted Sen. John Thune, a member of the GOP leadership team. "We don't have a lot of margin for error," Thune said.
Thune subtly offered some advice to the 2016 candidates.
"Our guys understand that their success in running for president is predicated, I think, as well, on us being able to function effectively and to get some things done here in Congress," he told reporters in the Capitol on Wednesday. "That will be the bigger picture, and I hope that that's what animates their actions and the things that they say around here."