Another impact is going to be Gephardt's STRONGLY held views on two (2) issues near and deep to America Left (yes, small but powerfull in the Democratic party and critical in several "leaning states."
1. Iraq, Gephardt stood then (and still does) by his Iraq War vote. While he is was critical on the post fall of Baghad conduct of the war, I doubt he'll do a Edward's reversal.
1a. Gephardt supports the Patroit Act and support GWOT loudly.
2. Taxes, he's a tax reformer/cutter, once again while overshadowed by Iraq in 2004, undoing Republican tax policies (going back to Reagan and that arch-republican tax cutter JFK) was a demand of the MoveOn types.
So while gaining votes (maybe even mind, I supported Gephardt in the primaries), how many does he lose from the hard core left... Plus the possible convention scrap and the tears (and interviews) from the left's media stars.
My guess, Gephardt puts in play;
OTL Bush Win;
New Mexico/ 5
Iowa/ 7
Colorado/ 9
Missouri 11 (easy win OTL, but Gephardt is still very much the favored son)
Ohio 20 (maybe, i susspect Kerry got every vote, and a few more, that he was going to get in Oh)
But OTL Kerry Win how in play/ lean Bush;
Wisconsin /11
New Hampshire/ 4
Minnesota/ 10
Penn/ 21 (OTL Kerry's people worried abt Penn till the last day)
Plus Gephart while Gephardt won't lose the West Coast for Kerry, much like in 2000, he forces Kerry to campaign (read spend money) there while not giving Bush the same headacne in the South and midwest.
Swinging everything but PA and OH, get a 7 vote gain, not enough. Especially if Gephardt on the ticket casues Bush/Cheney to fight the end, instead of coasting (and focusing on the House races) the last two week as in our OTL
In the end it's a push.