The difference between red and blue is often about 5-10 percentage points. But if you're up 5, that means your opponent is down 5. Because it still has to add up to 100.

To turn a state green, that party would have to be up at least 50%.

You see how that's a problem, right?

But while Green is pushing ahead, where do you think those votes are coming from?

If the Greens pick up 5% of the vote, they need to take those votes from someone, and that's most likely the Dems. Now they have 45% of the vote, because percentages still have to add up to 100, the Republicans have 50%, and handily win the election.

For greens to replace, most likely the democrats, would involve the left loosing every election for about a decade or two. Just completely having no voice in government.

You see what parties don't switch like that right? No, the party has to collapse, and then a replacement has to step in.

And in order for a party to collapse, it needs to be a coalition party. Like the Whigs. https://www.history.com/news/whig-party-collapse

Something that is unlikely to happen to a modern party.

Thus the only way for the greens to gain power is to change the voting system. Real voting reform needs either Approval or STAR as the voting system. (there are a few more, like Ranked Robin, but the main point is that it needs to be a cardinal voting system.)

The Green party under Jill Stein mildly supports RCV, a system that deeply flawed and will not actually fix things.