Isn't it the other way around? The presidential candidate usually attracts votes to the candidates lower down on his party's ticket. At least that's the old traditional wisdom.
Every Conservative should run their own race and not try to tie themselves to a deeply flawed Presidential nominee (presuming the GOP doesn’t do the right thing and dump Willard).
It depends. Ohio doesn’t seem to split tickets as much as some other states. I think Brown is in a stronger position than Obama so I’d be surprised if Mandel won and Romney didn’t.
2004 South Dakota was an interesting case of coattails. Bush’s coattails helped pull Thune to victory. But Dashole brought out 105% of the Indian vote and they of course voted for Kerry too and helped South Dakota be one of only 3 states where Bush got a (in this case slightly) smaller total % of the vote than in 2000 (others were VT and NC, just barley, I guess thanks to Edwards).