Muskie fell victim to inferior organizing, an over-reliance on party endorsements, and Nixon's "dirty tricks" operatives, and in the March 7, 1972, New Hampshire primary, did worse than expected with McGovern coming in a close second. As Muskie's campaign funding and support dried up, Hubert Humphrey, who had rejoined the Senate, became McGovern's primary rival for the nomination, with Alabama governor George Wallace also in the mix after dominating the March 14 primary in Florida. --> McGovern won a key breakthrough victory over Humphrey and Wallace on April 4 in Wisconsin, where he added blue-collar economic populism to his appeal. He followed that by dominating the April 25 primary in Massachusetts. At that point, McGovern had become the frontrunner. A late decision to enter the May 2 Ohio primary, considered a Humphrey stronghold, paid dividends when McGovern managed a very close second there amid charges of election fraud by pro-Humphrey forces. The other two leading candidates for the nomination also won primaries, but Wallace's campaign in effect ended when he was seriously wounded in a May assassination attempt, and McGovern's operation was effective in garnering delegates in caucus states. The climactic contest took place in California, with Humphrey attacking McGovern in several televised debates; in the June 6 vote, McGovern defeated him by five percentage points and claimed all the delegates due to the state's winner-take-all rules. He then appeared to clinch the nomination with delegates won in the New York primary on June 20. However, Humphrey's attacks on McGovern as being too radical began a downward slide in the latter's poll standing against Nixon.