I've seen a lot of questions lately asking if the Republican Party is on the decline. Most people who ask this question focus on the fact that White Anglos are expected to become a minority in a few decades. Most answers I've seen suggest that the Republican party isn't in trouble due to this shift, but all of the ones I've seen completely ignore the fact that in 2020 60% of voters under the age of 30 voted Democrat, the largest margin of any age group, and a margin that has only been widening with each election. Does this mean that the Republican Party really is in trouble, and that the country is on the verge of become a one-party nation, or is it likely that more of these voters will vote Republican as they get older?
Shifting voting patterns doesn't mean the Republican party itself is in trouble, only its current political ideology. In the long term it means the Republican party will probably have to change to accommodate more voters.
Example of something which the Republican stance has shifted on.
In the period 1850–1870, the Republican Party was more opposed to immigration than Democrats, in part because the Republican Party relied on the support of anti-Catholic and anti-immigrant parties, such as the Know-Nothings, at the time. In the decades following the Civil War, the Republican Party grew more supportive of immigration, as it represented manufacturers in the Northeast (who wanted additional labor) whereas the Democratic Party came to be seen as the party of labor (which wanted fewer laborers to compete with). Starting in the 1970s, the parties switched places again, as the Democrats grew more supportive of immigration than Republicans.