King had hinted that he was eyeing the Senate seat held by Democrat Kirsten Gillibrand, and previously by now-Secretary of State Hillary Clinton, but today he said so far he is "leaning against" it. King told Stephanopoulos he will decide in the next week.
Why the change of heart?
King said he is inclined to keep his position in the House because if the Republicans regain control of that chamber in this year's mid-term election, it will make him the chairman of the influential House Homeland Security Committee, a position he enjoyed for two years before Democrats became a majority in the House in 2006.
Being chairman would "put me in a position to get more done," King said.
Democrats face a tough election fight this year.
They face the prospect of losing key seats in Congress, which could threaten Obama's agenda. The president enjoys a comfortable Democratic majority in Congress at the moment, and with concerns about some seats going into Republican hands, the White House is likely to push big agenda items such as health care, financial regulatory overhaul and climate change, all of which Republicans oppose.
Democratic lawmakers from Republican-leaning states also face a tough balancing act as they try to align their party's interests with that of their constituents.
ABC News' Jonathan Karl contributed to this report.