Retiring Sen. Tom HarkinTom HarkinDistance education: Tumultuous today and yesterday Grassley challenger no stranger to defying odds Clinton ally stands between Sanders and chairmanship dream MORE (D-Iowa) says Hillary ClintonHillary Diane Rodham ClintonBiden slams Trump over golf gif hitting Clinton Overnight Cybersecurity: Equifax hit by earlier hack | What to know about Kaspersky controversy | Officials review EU-US privacy pact Overnight Tech: Equifax hit by earlier undisclosed hack | Facebook takes heat over Russian ads | Alt-right Twitter rival may lose domain MORE should start visiting Iowa more if she plans on launching a 2016 presidential bid.

"If she's going to run, she should start getting out here," Harkin told the Quad-City Times on Friday.

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He touted Clinton as a strong candidate that "would bring a lot of experience and knowledge that we haven't had in that White House for a long long time. "I mean just from the git go ... I think she's proven herself over all these years," Harkin added.

The 30-year Senate Democratic veteran, who himself ran for president, also encouraged Maryland Gov. Martin O'Malley and Vice President Joe BidenJoseph (Joe) Robinette BidenBiden slams Trump over golf gif hitting Clinton Overnight Tech: Equifax hit by earlier undisclosed hack | Facebook takes heat over Russian ads | Alt-right Twitter rival may lose domain Overnight Finance: CBO to release limited analysis of ObamaCare repeal bill | DOJ investigates Equifax stock sales | House weighs tougher rules for banks dealing with North Korea MORE to stump in his state.

The race to replace Harkin in the Senate is heating up. Rep. Bruce Braley is the only Democrat in the race so far. Republicans include State Sen. Joni Ernst, businessman Mark Jacobs and former attorney general Matt Whitaker.