In most countries, you have many parties, each taking specific stances on issues. You can vote for a party knowing they would oppose aid to Israel. However, your party is unlikely to win an outright majority of seats in parliament, so they need to form a coalition with other parties to rule.
The thing about US Politics is that coalitions form into the parties. Just because you disagree with some high profile democrats doesn’t mean that other democrats don’t agree with you.