Does the changing American demographic picture spell doom for the Republican Party? Michael Barone isn’t convinced. He explains why in his latest column.

From the results of the 2008 presidential election, many pundits prophesied a bleak future for the Republican Party, and not implausibly.

The exit poll showed that President Obama carried by overwhelming margins two demographic segments that were bound to become a larger share of the electorate over time.

He carried Hispanics 67 to 31 percent, despite Republican opponent John McCain’s support of comprehensive immigration legislation. Obama carried voters under 30 — the so-called Millennial Generation — by 66 to 32 percent.

But over time, Democrats’ hold on these groups has weakened. In Gallup polls, Obama’s job approval among Hispanics declined from 75 percent in 2012 to 52 in 2013 and among Millennials from 61 percent in 2012 to 46 percent in 2013.

The recent Harvard Institute of Politics poll of Millennials showed Democrats with a big party identification edge among those over 25, but ahead of Republicans by only 41 to 38 percent among those 18 to 20.

The older Millennials came of political age during the late George W. Bush years and were transfixed by the glamor of candidate Obama in 2008.

The younger Millennials are coming of political age in the middle Obama years and are plainly less enchanted and open to the other party. …

… All these eddies and currents have the potential to shift the nation’s political focus and partisan balance, in various directions.

Any single, straight-line extrapolation, like those from the 2008 exit poll, risks missing the next turn in the political road.