Triple major - what would happen?

Business + political science + STEM subject is not a ‘trifecta’ of 3 separate fields- business & political science are both social sciences.

As @juillet says, what will matter much, much more than the majors listed on a resume is how the person has backed them up through work experience and any narrative arc. An incredibly obvious one would be the PoliSci + Business + Environmental Science student, who has done internships in a political office and in both the marketing and research divisions of a company that make, say, an superior widget for testing for biological contamination. But (imo) an Accounting + a Political Science + a Bio major who has worked at the DQ every summer will be at a disadvantage over a student with any one of those majors who has done internships in their field each summer.

So, OP if you are aksing 'would the fact of a triple major covering all 3 subjects in and of itself impress potential employers, I would agree with @juillet that the answer is essentially, no. The context will make all the difference.

@lurker323, I profoundly disagree with you on these points, and know plenty of single-major undergrads coming out and getting good jobs. They have used their time in college to get jobs and internships, to shape a direction so that their academic background + experience make them interesting to employers.

On the other hand, I agree that the problem of this:

is real, but the problem is not single majors. It is a combination of making a university degree the de facto standard for any and old jobs and really poor advising from secondary school onwards. When my parents went to college any college degree gave you a leg up - and there were only a fraction of the number of majors available. As my kids go to college they have 80-100 majors to choose from- not counting interdisciplinary and independent, and in many fields you need a Masters just to be considered for a job. College advisors at Big State U are there to get the kids through the college system first, not work out the employment prospects of any given major{s).