Hillary Clinton's focus on her Republican challengers may be much-needed as the Democratic frontrunner is trailing the leading GOP presidential hopefuls in key swing states, a Quinnipiac University poll revealed.

If the 2016 election were held today, Clinton would lose or tie for the presidency in Virginia, Iowa and Colorado -- states among whose voters the former secretary of state suffers "strikingly negative favorability ratings," the Washington Post noted.

In hypothetical matchups against Florida Sen. Marco Rubio, former Florida Gov. Jeb Bush and Wisconsin Gov. Scott Walker, Clinton was either clearly behind or, as Quinnipiac put it, "on the wrong side of a too-close-to-call" race, according to Fox News.

The most significant gap was observed in Colorado, where Walker beat Clinton by 9-percentage points (47 percent vs. 38 percent), Rubio by 8 points (46 percent vs. 38 percent) and Bush by 6 points (42 percent vs. 36 percent). President Barack Obama carried the Centennial State's nine electoral votes both in 2008 and 2012.

In a number of contests, meanwhile, Vermont Sen. Bernie Sanders does as well as -- or even better than -- Clinton against Rubio, Bush and Walker, Quinnipiac University detailed. Many observers consider Sanders to be the only Democratic presidential hopeful who can hope to mount a serious challenge to the former first lady. Sanders' advantage over the GOP candidates, however, does not extend to Vice President Joe Biden, who at times has toyed with joining the 2016 White House race.

Peter Brown, the assistant director of the university poll, meanwhile, noted that Clinton's challenges have deep roots.

"She has lost ground in the horserace and on key questions about her honesty and leadership," Brown explained. "On being a strong leader, a key metric in presidential campaigns, she has dropped four to 10 points depending on the state and she is barely above 50 percent in each of the three states."