Howard Dean (D) is heading to Iowa, a decision that raises questions about a possible White House bid.

The former Vermont governor and presidential candidate, who has said he's open to running for the White House again in 2016, will headline an event for the Iowa Federation of Labor on Aug. 21, according to an aide at Democracy for America, a group founded by Dean and run by his brother.

Dean was encouraged to attend by 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), who endorsed his 2004 presidential campaign, according to the aide. 

His speech will focus on DFA's "Purple to Blue" program to win back statehouses lost in the 2010 election. The group is currently targeting Virginia, and the DFA spokesman says Iowa is high on its target list for 2014.

The former governor has also been critical of former Secretary of State and former presidential hopeful Hillary ClintonHillary Rodham ClintonAssange meets U.S. congressman, vows to prove Russia did not leak him documents High-ranking FBI official leaves Russia probe OPINION | Steve Bannon is Trump's indispensable man — don't sacrifice him to the critics MORE, predicting she'll face a primary challenge from the left if she runs for president.

"He's never taken it off the table," the DFA aide said of Dean's potential presidential run. "No matter what there's going to be a primary in 2016 and it's going to be critical for Democrats to nominate a progressive candidate who's willing to stand up and fight for the issues that matter to the majority of Americans, whoever that candidate is."

Dean led polls of Democratic voters for a time before the 2004 Iowa caucuses, where he placed a disappointing third.