Asked by an audience member what she would say to Sanders supporters who might be hesitant to support her candidacy, Clinton encouraged them to support her, but had a stern message for potential holdouts.
"I think it's very dangerous to look at the alternatives and believe that your staying home is a responsible choice," Clinton said. "It's hard for me to believe that anybody who would support Senator Sanders would want to see any of the Republicans elected president of the United States.
"I would just ask that when this nomination is wrapped up that they come and join with us to make sure that we don't turn the White House back over to the Republicans," she added.
The tensions between the Clinton campaign, the Sanders campaign and the Democratic National Committee have recently been at their highest point, thanks largely to a data breach that left the Sanders campaign accused of stealing the Clinton campaign's data.
Sanders and his campaign alleged that the DNC suspended their access to their campaign's data in an attempt to sabotage their campaign. And over the weekend, Sanders said that the timing of the primary debates -- which included several little-watched weekend events -- was intended to "protect" Clinton.
Here in Iowa, Clinton has consistently polled ahead of Sanders. But the Clinton campaign insists that they are taking nothing for granted.
Her visit to two small Iowa towns in Southeast Iowa on Tuesday marks her 20th campaign day in the state before its Feb. 1 primary, and her final visit to the state in 2015.
In Fairfield, Clinton acknowledged that many progressives back Sanders because they believe that she is not progressive enough. But, she noted: "I'm a progressive that likes to get things done."
"On a lot of issues, I think that I have staked out a progressive set of policies that go way back to before my time in elected office," Clinton said.
She warned also that if disillusioned Democrats stay home in the general election because they feel that she fails a purity test, the Republican alternative would be far worse.
"I have no sympathy for those who would then decide that they're going to pass after they've expressed themselves because whoever the alternative is, is not pure enough, is not able to fulfill the hopes that we all have," Clinton said. "Politics is hard and it is something that is not for the weak of heart."
Republicans "would be thrilled if people who are progressive decide to stay home," Clinton added. "They will do everything they can to try to make that happen."