By doing whatever they can to undermine free and fair elections — gutting net neutrality, false voter “fraud” comissions, demonizing the press, voter ID “laws,” etc. basically doing whatever it can to make sure that only older white men are voting.
Some of this stuff can impact elections on the margins, but there's not a lot of evidence any of these things have really changed the outcome of many races.
The first two things you mentioned may end up impacting "free and fair elections" in the future, obviously those would be new developments and haven't had the chance to impact any election yet. I'm not sure how "demonising the press" would prevent a free and fair election...that's a standard tactic the GOP has been doing (and in some cases Democrats, especially the Clintons) for decades. And in any event such behaviour is clearly protected by the first amendment, and always will be.
As for voter ID laws, yes they can be discriminatory, and there's not a lot evidence that voter fraud really impacts elections, but despite the hype
there's also no conclusive evidence that they have
any great impact on elections either. For example, Clinton's claim that voter ID laws cost her Wisconsin are almost certainly
not true. Similar flawed methodology makes up most of the claims you see on Facebook and Twitter that voter ID laws are swinging a lot of elections.
With regards to gerrymandering...all that gerrymandering that went on after 2010 has almost certainly enabled the GOP to hold onto more seats and put them in an electoral advantage, but gerrymandering only explains so much. Let's remember that a large number of the GOP gains in legislative races over the past decade came in 2010,
before their gerrymandering came into effecting. In other words, Republicans won big in 2010 under the
exact same district lines that allowed the Dems to win big in 2006. After the 2010 elections (and before redistricting) Republicans controlled 242 seats in the Congress vs. 193 for Democrats….essentially where it is today,
after the 2010 redistricting. And of course gerrymandering doesn't factor at all into the many state wide races the GOP has won over the past decade.
I understand the temptation for Democrats to blame their losses on stuff like this, it's easier than diagnosing the real problems the party has. But blaming all their woes on voter ID and gerrymandering isn't going to win them much of anything. Obviously, Republicans have their own deep, deep problems as a party as well, but so far those problems haven't prevented them from winning that much (two terms of Obama excepted). Things like having good candidates, a deep bench, and a coherent message still account for the bulk of the reasons elections are won and lost. And the other variables, like the out of power party doing well in off year elections, explain poll results more reliably than things like voter fraud & suppression.
Finally, with regards to the GOP only wanting 'older white men' to vote, I'm not sure that's true. Republicans usually win among white women and middle aged men as well, and enough of younger white men...and certainly could not win without those groups. Just as Democrats could not win without the votes of their key demographics.
