WASHINGTON — Before cable television, Netflix, YouTube and other attention-grabbers on the Internet, American presidents had little competition for viewers when they delivered their annual State of the Union address. But, oh, how the big night has changed.Sure, the pageantry and theatrics of the annual presidential address will all be there when President Barack Obama stands before a joint session of Congress with a stem-winder of a speech Tuesday night. There will be standing ovations from his supporters, and strategic smirks and scowls from his opponents. Along with wall-to-wall media coverage and cable news countdown clocks.But viewership is falling, with 20 million fewer people watching last year’s State of the Union compared to Bill Clinton’s address at the same point in his presidency. Congress rarely follows through on the policy proposals the president unveils. And this year, the battle lines between Obama and the new Republican-led Congress will have already been set before the president arrives on Capitol Hill for the annual address to a joint session of Congress and a television audience of millions.The dwindling impact of the big speech has sent the White House searching for new ways to break through. It’s now thinking of the State of the Union as an “organizing principle” rather than a single, communal event.So instead of waiting until Tuesday night’s address to announce new initiatives, Obama has spent the past two weeks unveiling them in a series of speeches around the country and social media posts. The White House is aiming to get people who don’t tune in to the 6 p.m. PST address to catch up with at least parts of it later. And the president’s first big post-speech interview will go not to a big newspaper or TV network but to YouTube, in hopes of capturing the attention of some of those less likely to have watched the actual speech.