Collins winning Maine is a HUGE relief to me. I was more concerned about the Senate than the Presidency, what with Democrats threatening to expand the Supreme Court (because they are used to the Court going there way for decades on major issues, such as abortion and Obamacare, and they can't tolerate it being origanalistic-leaning for once) and threatening to add states to the union just to give themselves a perpetual advantage going forward in the Senate (D.C. and Puerto Rico). D.C. should just rejoin a state if they are so desperate to be counted towards the senate. Their lands were literally taken out of existing states, not like they were settlers moving into untamed lands, so if they want statehood they should vote to remerge with another state like Maryland, where they will have other like-mindedly liberal individuals and they can all be happy together. And Puerto Ricans are pretty divided on what they want to do so I doubt they could all get behind that anyway.
Anyway, with Alaska and the two Georgia races going Republican (at least I'm assuming based on numbers so far), looks like Republicans will keep control of the Senate with at least 51, possibly up to 52 or 53. Collins is a moderate, so she will no doubt confirm Biden appointed justices (which, worse case for conservatives, means 50-50 tie in the Senate with Harris being the tie breaker). What this means going forward, if Biden wins (which I expect him to at this point):
1) Biden won't get anything done that isn't bipartisan for at least 2 years. Honestly he's probably happy with that. I don't think Biden particularly likes Sanders/Warren/AOC. I get the impression, on core issues, he feels more in line with moderates in his party (regardless of what he says on TV to appease the socialists). And the only way he is getting anything done is if he can get Collins on board, and not lose vulnerable votes from democrats in red/purple states concerned about their own re-election chances in 2-4 years (Manchin, Sinema, Tester). That's at least 4 moderates he will have to appease to get things done. None of those four do I anticipate voting for huge environmental reform bills, or massive government spending on new programs. Because of this, I suspect Biden's first 2 years, and possibly his entire first term, will be mostly a "chill" presidency, which may be what we all need anyway haha. 4 years of nothing happening would probably calm people down some.
2) The chances of Harris invoking the 25th amendment just decreased. She won't have the backing of the Senate to enact extremely liberal policies, which will make losing moderate Democrats support when she runs for re-election (by betraying Biden) less "worth it" in the short term, as she won't be able to accomplish much. Unless Biden literally can't do the job, I don't think he will be removed from office. And if he does get removed, I suspect Harris to nominate a moderate as her VP to balance it out. If Democrats had picked up enough of the Senate to give them, say, a 53-47 lead with Harris, I suspect Harris would 25th amendment Biden, nominate an ultra liberal as her VP, and do whatever she wants for at least 2 years.