Oh, they'll make it worse... but will they, really? Or do you just have to believe that so you can go on believing the Democrats are the last, best hope for humanity?
I recall in 2000 going to see Ralph Nader speak. He opened his talk by saying "Let me tell you a few things about our next President" and then rattled off a whole list of things that would be true, or that wouldn't change, whether George W. Bush or Al Gore was elected. I can't remember any of his bullet-points now, but I remember that everything he said made sense, and I was nodding in agreement with almost everything he said.
And then September 11th happened, and in response, our whole country went [flipping] insane and the Bush Administration launched a war with Iraq, apropos of nothing. Probably Al Gore would've sent troops into Afghanistan. But Iraq? Unless Gore has said so in the years since, I don't think he would've invaded Iraq.
So if you ever notice me rolling my eyes and brushing off people who claim it doesn't matter who we vote for, this is why.
And let me just cut off anyone who wants to start flapping their gums about me letting the Dems off the hook. I'm not and I never have. It was before I was on this site, but in the handful of election cycles after 2003, I told anyone who would listen - and probably quite a few who weren't listening

- that they should look up the members of Congress who voted for the invasion and vote them out of office, regardless of which party they want to support (I mean, I'd have preferred that people elect Democrats, but baby-steps...). I also resented having Hilary Clinton shoved down my throat. I was thrilled to be able to vote against her in the 2008 primary, and was aggravated that I had to do it again in 2016. (I mean, WTH is wrong with the Democratic Party?
We don't want Hilary Clinton. Hello? Is this thing on?) I remember chatting with a friend in 2015 and saying, "If Clinton gets the nomination, I don't know what I'm going to do." Then Donald Trump made my decision super easy. I guess I can thank him for resolving that conundrum for me, if nothing else.
Almost definitely, yeah. There's really no situation so bad the GOP can't make it worse.
x36,784*
* That's the number of Americans killed and wounded in Iraq, according to NBC News. If someone wants to use the number of Iraqis killed instead, good luck, there doesn't seem to be an agreed-upon figure yet. If you wanted to get into the economic costs of the war, that's also still unsettled, but everyone seems to agree it's north of a trillion dollars, just for the United States. The 2008 book by Joseph Stiglitz and Linda Bilmes, in which they tried to project out the ultimate cost of the invasion of Iraq to the U.S., was titled The Three Trillion Dollar War. And that was years before the emergence of ISIS, to name just one aftershock. I don't know if they've revised their estimate in the last ~15 years, but if they have, I doubt it went down.
EDIT: I forgot, that 36,784 also doesn't count the 30,000 veterans who served after 9/11 who've committed suicide (30,000 as of a study published in 2021, so it's got to be more than that now). That number would include those who served in Afghanistan and elsewhere, not just Iraq, but obviously a lot of them must have served in Iraq. I think people who were on active duty during those years had a good chance of being deployed to both theaters at some point. I remember being at an anti-war rally in 2003-2004 (there were maybe 200 people there) and somebody driving past shouted "Support the troops!" We responded by shouting, "We are!" I don't know if that guy was shouting in solidarity with us, or if he thought he was rebuking us. If it was the latter, I wonder if he and people like him ever came to understand what we meant, or if they still think supporting our troops means sending them to war. Literally the other day I heard a story on the radio about veterans struggling to get their VA medical benefits (because, among other things, they have to prove that their medical problems were actually incurred during their term of service - I guess they don't just get healthcare as payment for having served the country). You want to support the troops? Voting for socialized healthcare would be a place to start.