There's the flaw in your reasoning.
The flaw is the stubborn unwillingness of some conservatives to believe in hard facts. Bush lost PA, for example, even though the pro-lifers backed him to the hilt. And this was even though even the Amish—who rarely vote—came out in record numbers to support him. To think Toomey, an unknown, would have done better than Bush in PA is wholly unreasonable.
Nope, there is no flaw... Snowballs have better chances in hell than Toomey had of surviving the Philly voters and winning a statewide run in 04.
You got that right! The Dem candidate was so weak, the Democrat party was perfectly willing to sell him out and swing votes to Specter! (Remember the Rendell/Specter election signs that mushroomed all over PA?) They would not have done that had Toomey been the nominee, but Toomey would have had the grassroots of the Republican party behind him.