Ryan: Yes, was keynote speaker for Iowa GOP's big fundraising dinner in Cedar Rapids in April. Main speaker at governor's annual birthday fundraiser in November 2013, in first visit since 2012 campaign.
Santorum: Yes, state GOP conference in June, earlier visit with strategists and media. Also August 2013 speech to conservative Christians in state where he won the 2012 caucuses. Screened his new Christmas movie in Iowa in November.
Walker: Yes, fundraiser last year.
GO TO NEW HAMPSHIRE: Nation's first primary comes after Iowa and is just as important.
Biden: Yes, raised money for three Democrats in March visit for job-training event. Quipped: "I'm here about jobs — not mine."
Clinton: No. But Ready for Hillary has sent people there this year.
O'Malley: Yes, spoke at Democratic Party dinner in November, returned in June. Also spoke at 2012 convention of New Hampshire Democrats.
Christie: Yes, in June, to help candidate for governor, after a long absence. Visited three times in 2012.
Cruz: Yes, three times since August 2013.
Jindal: Yes, keynote speech to local Republican organization in March, headlined state GOP fundraiser in 2013, visited twice in 2012.
Paul: Yes, addressed Freedom Summit in April. Won straw poll at March meeting of Northeast Republican Leadership Conference in Nashua. Several visits last year.
Perry: No, but had group of 13 conservative leaders from the state to Texas for private meeting in May.
Rubio: Yes, splashy debut in May, first visit of the 2016 season, headlining fundraisers, meeting local officials, giving interviews. Multiple visits before 2012 election.
Ryan: Yes, headlined Manchester fundraiser in February for former House colleague. Canceled October 2013 visit because of government shutdown.
Santorum: Yes, March speech to Northeast Republican Leadership Conference marked his return to a state where he performed weakly in 2012 campaign.
Walker: Yes, headlined a GOP state convention in October 2013, keynote at state party convention in September 2012.
DON'T FORGET SOUTH CAROLINA: First Southern primary and big in its own right.
Biden: Yes. In May, gave commencement speech at University of South Carolina and headlined Democratic fundraiser, first visit since he spoke at state party's annual fundraiser a year earlier. Several earlier visits since 2009.
Clinton: No, but things are stirring. At a May meeting in Columbia partly sponsored by Ready for Hillary, Virginia Sen. Tim Kaine urged Democratic women to "think about pledging your support right now" to ensure she has "millions of us ready to take the field with her" if she runs.
O'Malley: Yes, in May to campaign for state Sen. Vincent Sheheen, Democratic candidate for governor. Also made a 2013 speech to Democratic activists.
Bush: Yes, 2012 speech.
Christie: Summer visit expected, to raise money for Gov. Nikki Haley. Came in 2012 on behalf of GOP presidential nominee Mitt Romney.
Cruz: Yes, speech at The Citadel military college in April was third visit in a year, following event with religious conservatives in November and speech to annual state GOP dinner last May.
Jindal: Yes, made third visit in a year in June, as keynote speaker at state GOP's biggest gathering, the Silver Elephant dinner.