LEXINGTON, Ky. -- The fierce fight to win Kentucky's Senate seat carries with it some lingering intrigue: the complicated relationship between a potential future president and a potential future majority leader.

In one corner, Senate Minority Leader Mitch McConnell (R-Ky.) is running his campaign squarely against President Obama -- whose favorability remains below 30 percent here -- instead of his youthful, energetic challenger, Kentucky secretary of state Alison Lundergan Grimes (D). In the other corner is the Grimes campaign, which has practically ignored Obama's existence -- as a stand-in for the actual nominee used the Clinton family as the de facto challenger to McConnell.

That dynamic reached a crescendo Saturday afternoon inside a packed theater on Transylvania University's campus here, when former U.S. secretary of state Hillary Clinton delivered a 22-minute rallying cry for the 35-year-old challenger -- the seventh time she or former president Bill Clinton have appeared in Kentucky for Grimes.

Clinton accused Republicans of running a campaign of "fear," suggesting McConnell's campaign had been endlessly negative in an attempt to smear the challenger. McConnell aides "just hope that enough of it sticks," she said.

But not once did she ever mention the Senate minority leader by name.

"If Alison's opponent wanted to run against the president, he had the chance in 2012," Clinton said, to cheers from more than 1,200 Democrats packed inside the event.

It was a delicate bit of diplomacy for Clinton, honed both in her four years at Foggy Bottom and her eight years serving alongside McConnell in the Senate. Local observers say that former president Bill Clinton has no hesitation in invoking McConnell by name -- but Hillary Clinton seems to avoid it.

It's likely, at least in part, senatorial courtesy -- but also it could help smooth relations between the two should Hillary Clinton run for, and win, the presidency in 2016. Polls show McConnell with a small-but-steady lead, and Republicans are very close to securing the six seats necessary to win the Senate majority in Tuesday's elections.

That would make McConnell the majority leader, a post he might still hold if and when Clinton is sworn in as president in January 2017. The Republicans will face a difficult electoral map for the Senate in 2016, so GOP strategists are hoping for a big sweep that will provide a cushion for seats they could lose two years from now and maintain the majority.

For his part, McConnell denies that he holds any grudge against the Clintons for their overt stumping for Grimes.

"I don’t think it’s personal, it’s just business. This is the Clintons' business., to go around the country. The president’s so unpopular that the only person they can send out that everybody’s heard of is President Clinton," he said Friday after a stop in Lexington, adding again: “It’s not personal.”

Still, he declined to say whether any grudges would linger if he had to negotiate with a President Hillary Clinton. “I’m hoping that doesn’t happen and we don’t have to figure out," he said.

In 2010, McConnell hosted Hillary Clinton at the institute he built at his alma mater, University of Louisville, for a lecture that followed his tradition of bringing in a bipartisan collection of speakers, including Vice President Biden and the late Edward M. Kennedy (D-Mass.). At that event, still serving as secretary of state, Clinton praised McConnell's work on foreign policy, which The Hill newspaper noted last month in this lengthy quote from her 2010 speech:

"I was fortunate to find common cause and work with him on a number of foreign policy issues: human rights in Burma; legislation to support small businesses and micro-credit lending in Kosovo; promoting women and civil society leaders in Afghanistan; strengthening the rule of law in parts of the Islamic world. ... And I’ve appreciated working with him in my new capacity upon becoming secretary of State."

The Clintons are longtime friends with Jerry Lundergan, the father of the candidate and a former state party chairman who helped deliver the Bluegrass State twice for Bill Clinton. Grimes frequently labels herself a "Clinton Democrat," and over a memorable stretch a few weeks back she refused to acknowledge whether she had even voted for Obama.

That connection is the main factor driving their support for Grimes, it seems. But there's a chance that the Clinton-McConnell relationship could prove to be a longtime determinant of national policy.

"Tuesday is your chance to reject the guardians of gridlock," Hillary Clinton said Saturday, drawing the activists to their feet.

If voters don't take her advice, and McConnell wins, the "guardian of gridlock" could play a key role in shaping the success or failure of the next Clinton administration.